<template>
  <div class="spec-preview">
    <img v-if="skuImageList[currentIndex]"  :src="skuImageList[currentIndex].imgUrl" />
    <div class="event" @mousemove="move"></div>
    <div class="mask" ref="mask"></div>
    <div class="big">
      <img v-if="skuImageList[currentIndex]" ref="bigImage"
           :src="skuImageList[currentIndex].imgUrl"/>
    </div>
  </div>
</template>

<script>
  import {mapGetters} from "vuex";
  export default {
    name: "Zoom",
    data(){
      return {
        currentIndex:0
      }
    },
    computed:{
      ...mapGetters(["skuImageList"])
    },
    methods:{
      move(event){
        //代表  maskDiv最终要产生的位移
        const maskDiv = this.$refs.mask;
        const bigImage = this.$refs.bigImage;
        let left = 0;
        let top = 0;

        //触发mousemove事件时 鼠标距离event.div paddingbox的偏移量
        const {offsetX,offsetY} =event;
        const width = maskDiv.offsetWidth;
        //计算left & top的实时值
        left  = offsetX - width/2;
        top  = offsetY - width/2;

        //处理一下left & top的边界情况
        left < 0 ? left = 0 : "";
        left > width ? left = width : "";
        top < 0 ? top = 0 : "";
        top > width ? top = width : "";

        //获取mask dom节点
        maskDiv.style.left = left + "px";
        maskDiv.style.top = top + "px";
        bigImage.style.left = -2*left + "px";
        bigImage.style.top = -2*top + "px";
      }
    },
    mounted(){
      this.$bus.$on("getIndexForZoom",(index)=>{
        this.currentIndex = index;
      })
    }
  }
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }

    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }

    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    .event:hover~.mask,
    .event:hover~.big {
      display: block;
    }
  }
</style>
